It is known that a silicone elastomer sheet, such as a silicone rubber sheet or silicone gel sheet, can be used as the sheet employed to bond a liquid-crystal display panel to a transparent protective sheet therefor with the goal of improving the impact resistance and visibility of small liquid-crystal display devices (e.g., handheld game players and cellular phones), liquid-crystal displays (e.g., for personal computers), and large liquid-crystal display devices (e.g., liquid-crystal televisions). With regard to silicone rubber sheets that exhibit adhesiveness, for example, Japanese Laid-Open (Kokai or Unexamined) Patent Application Number Hei 8-143834 (143834/1996) describes a silicone rubber adhesive sheet in which the following are layered in the sequence given: separator, layer of adhesive, polyethylene terephthalate film, primer layer, and silicone rubber sheet. With regard to silicone gel sheets that exhibit adhesiveness, Japanese Laid-Open (Kokai or Unexamined) Patent Application Number 2001-200221 (200221/2001) describes a silicone gel adhesive sheet in which the following are layered in the sequence given: separator, layer of adhesive, substrate sheet, silicone gel sheet, and separator. With regard to silicone rubber sheets that do not exhibit adhesiveness, Japanese Laid-Open (Kokai or Unexamined) Patent Application Number 2002-287119 (287119/2002) describes a silicone rubber sheet that has a surface roughness (Ra) of 5 μm or less.
The former silicone rubber sheet and the silicone gel sheet have presented the problem of a complex structure because the layer of adhesive is different from the silicone rubber (or gel) layer and the silicone rubber (or gel) layer does not itself exhibit a satisfactory adhesiveness. The latter silicone rubber sheet has presented the problem of a weak adhesiveness.
Within the sphere of silicone elastomer sheet that itself exhibits adhesiveness, Japanese Laid-Open (Kokai or Unexamined) Patent Application Number Hei 6-200159 (200159/1994) describes an adhesive silicone rubber sheet that is afforded by the cure of an organoperoxide-curing silicone rubber composition comprising: 100 parts by weight of a dimethylpolysiloxane that lacks silicon-bonded alkenyl and that has an average degree of polymerization (DP) of 5,000 to 9,000, and 50 to 150 parts by weight of a diorganopolysiloxane that contains at least two silicon-bonded alkenyl in each molecule and that has an average DP of 3,000 to 7,000 that is also lower than the average DP of the above-mentioned dimethylpolysiloxane, and an organoperoxide.
The decomposition residues from the organoperoxide, however, can cause problems in the case of the oraganoperoxide-crosslinked adhesive silicone rubber sheet. While the hydrosilylation reaction does not produce such by-products, hydrosilylation-cured adhesive silicone elastomer sheet whose surface exhibits a stable and permanent adhesiveness has remained unknown.
It is an object of this invention to provide a hydrosilylation-cured adhesive silicone elastomer sheet that is transparent and whose surface exhibits a stable and permanent adhesiveness.